As LSI circuits are increasing in density, circuit linewidths required of semiconductor devices are becoming finer year by year. Formation of a desired circuit pattern on such a semiconductor device needs a high-accuracy original pattern (also called a reticle or a mask). The high-accuracy original pattern is produced using electron beam lithography technology with an electron beam writing apparatus.
The electron beam writing apparatus includes an electron gun, a blanking aperture member, a first shaping aperture member, a second shaping aperture member, a shaping deflector, and an electron lens for focusing an electron beam. An electron beam emitted from the electron gun is applied to the first shaping aperture member through the blanking aperture member. A first shaped aperture image formed by the first shaping aperture member is formed on the second shaping aperture member and is deflected by the shaping deflector. The first shaped aperture image optically overlaps the second shaping aperture member, so that the electron beam can be varied in size and shape. The resultant electron beam shaped in basic unit graphical form, such as a rectangle or a triangle, is applied to a target mask with high accuracy, thus writing a pattern.
An aperture member, such as the first shaping aperture member or the second shaping aperture member, is produced as follows: First, a resist applied to a front surface of a wafer substrate is patterned with an aperture shape (corresponding to an opening) by the electron beam writing apparatus. Next, the front surface of the wafer substrate is subjected to processing, such as development and etching, thus forming a first recess having the aperture shape in the front surface. Then, a rear surface of the wafer substrate opposite the first recess is subjected to back-etching to form a second recess such that the second recess communicates with the first recess, thus forming the opening extending through the wafer substrate. After that, the wafer substrate is subjected to dicing, or cut into a predetermined sized piece having the opening, thus producing the aperture member.
As described above, electron beam lithography has conventionally been performed for each formation of an aperture member. In producing a plurality of aperture members, the aperture members tend to have variations in aperture opening shape, leading to low reproducibility. Furthermore, since the produced aperture members each have a size of approximately several mm square, it is difficult to check accuracy of a pattern shape of each of openings in such small members by measurement with a dimension measuring device and a position measuring device.